GENOME ANALYSIS OF THE FUNGAL PLANT PATHOGEN, LEPTOSPHAERIA-MACULANS USING PULSED-FIELD GEL-ELECTROPHORESIS

Pulsed field gel electrophoresis (PFGE), or electrophoretic karyotypin g, separates chromosomal-sized pieces of DNA in agarose gels where the orientation of the electric field is periodically altered. This techn ique has revealed that many fungi have a high degree of chromosomal le ngth polymorphisms. Often the only isolates with identical karyotypes are derived from a single clone, thus PFGE provides a 'genetic fingerp rint' for them. The size range and number of chromosomes within isolat es of a particular species are usually constant, hence PFGE can distin guish between morphologically similar fungi. This technique can also b e used to follow inheritance of chromosomal length polymorphisms and s hows that in some fungi novel-sized chromosomes are produced during me iosis. As well as resolving the nuclear (A-type) chromosomes, it can a lso resolve dispensable (B-type) chromosomes and cytoplasmic genomes i ncluding mitochondrial DNA and linear plasmids. The application of thi s technique to Australian isolates of Leptosphaeria maculans, which ca uses blackleg disease of canola (Brassica napus), is discussed.